Plasma processing apparatus and method

ABSTRACT

A plasma processing apparatus ands a plasma processing method of excellent mass production stability by controlling deposition films deposited on the wall of a vacuum vessel are provided. This apparatus comprises a gas ring forming a portion of a vacuum processing chamber and having a blowing port for a processing gas, a bell jar covering a portion above the gas ring to define a vacuum processing chamber, an antenna, disposed above the bell jar, for supplying RF electric fields into the vacuum processing chamber to form plasmas, a sample table for placing a sample in the vacuum processing chamber, a Faraday shield disposed between the antenna and the bell jar and applied with an RF bias voltage, and a deposition preventive plate attached detachably to the inner surface of the gas ring excluding the blowing port for the processing gas. The area of the inner surface of the gas ring including the deposition preventive plate that can be viewed from the sample surface is set to about ½ or more of the area of the sample.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a plasma processing apparatus and a plasma processing method and, more particularly, it relates to a plasma processing apparatus and a plasma processing method capable of suppressing occurrence of obstacles caused by reaction products.

[0002] Materials to be etched which are used in the field of semiconductor device production can include volatile materials such as Si, Al and SiO₂, for example, for DRAM (Dynamic Random Access Memory) or logic circuit IC. Further, non-volatile materials such as Fe have been adopted for FRAM (Ferroelectric Random Access Memory) or MRAM (Magnetic Random Access Memory)

[0003] The non-volatile materials are difficult to be etched since the melting point of reaction products formed during etching is high. Further, since the vapor pressure of the reaction products after etching is low and the deposition coefficient to the inner walls of vacuum vessels (vacuum processing chamber) is high, the inner walls of the vacuum vessels are covered with deposits of the reaction products even after processing only a small amount of samples (several to several hundred of sheets). Further, when peeled and fallen, the deposits form obstacles.

[0004] When the reaction products are deposited, the coupling state between induction antennas and plasmas in the reactor changes to vary, with time, the etching rate or the uniformess thereof, vertical etching property, deposition states of reaction products on the etching side wall, etc.

[0005] Concrete examples of the non-volatile materials can include Fe, NiFe, PtMn, and IrMn as ferromagnetic or anti-ferromagnetic materials used for MRMA or magnetic heads, as well as Pt, Ir, Au, Ta, and Ru as noble metal materials used for capacitor portions or gate portions in DRAM, capacitor portions in MRAM and TMR (Tunneling Magneto Resistive) elements in MRAM. In addition, they can also include Al₂O₃, HfO₃, and Ta₂O₃ as highly dielectric materials, and PZT (Lead Titanate Zirconate), BST (Barium Strontium Titanate) and SBT (Strontium Bismuth tantalate).

[0006] Further, also in the field of semiconductor device production, a technique of forming Si, SiO₂ or SiN films by a plasma CVD method has frequently been adopted as production steps for semiconductor devices. In this technique, a polymerizable gas such as monosilane is injected into plasmas to form films on a wafer. In this process, a great amount of polymer films are deposited on the inner wall of a reactor other than the wafers to inhibit mass production stability. That is, when polymer film is deposited to an excessive thickness on the inner wall of the reactor, the polymer film is peeled and fallen from the surface of the inner wall and adhered on the wafer as obstacles in the same manner as described previously. Accordingly, it is necessary to conduct plasma cleaning by using a violent special gas such as NF₃, or manual cleaning conducted after opening the reactor.

[0007] In addition, in the field of semiconductor device production, a SiO₂ plasma dry etching step is used frequently. In the etching, fluoro carbon such as C₄F₈, C₅F₈, CO, CF₄ and CHF₃ is used as an etching gas. Reaction products formed by reaction of such gas in the plasmas contain a great amount of free radicals such as C, CF, C₂F₂ and, when the free radicals are deposited on the inner wall of the reactor, they cause occurrence of obstacles like the case described previously. Further, when the free radicals are evaporated again in the plasmas, they change the chemical composition of the plasmas to vary the wafer etching rate with time. Induction type plasma processing apparatus in which coiled antennas are disposed on the outer circumference of a vacuum vessel or plasma processing apparatus in which a microwaves are introduced into the vacuum vessel have been known as existent plasma processing apparatuses. In any of the processing apparatuses described above, since countermeasures for the deposited matters on the inner wall of the vacuum vessel in a case of etching the non-volatile material is not completely effective, a manual cleaning operation by opening the vacuum vessels to atmosphere is conducted repeatedly. Since manual cleaning requires as much as 6 to 12 hours from the start of the cleaning to the start of the processing for the succeeding sample, this lowers the operation efficiency of the apparatus.

[0008] For example, Japanese Patent Laid-open Nos. 10-275694, 11-74098 and 2000-323298 disclose plasma processing apparatus in which plasmas are generated by an induction method in a processing vessel, a Faraday shield is formed between induction antennas disposed on the outer circumference of a vacuum vessel and plasmas, and an RF power source is connected to the Faraday shield to supply electric power, thereby reducing deposition of reaction products to the inner wall of the vacuum vessel, or enabling cleaning for the inner wall of the vacuum vessel.

[0009] This apparatus is effective for, of the vacuum vessel, the portions that formed of a non-conductive material such as ceramics or quartzes and that effective electric fields due to the Faraday shield can reach. However, the apparatus is not effective for other portions formed of non-conductive material or conductive materials.

[0010] As has been described above, when reaction products are deposited excessively on the inner wall of the vacuum vessel, deposited films are peeled and fallen from the surface of the inner wall and adhered as obstacles on the wafer. Further, in the plasma processing apparatus using the induction antennas, the coupling state between the induction antennas and the plasmas in the reaction vessel is changed to vary the etching rate and the uniformess thereof, the vertical etching property, and the deposition state of the reaction products to the etching side wall. Further, when the inner wall of the vacuum vessel is cleaned, since it takes much time till the start of the processing for the succeeding sample, the operation efficiency of the apparatus is lowered. Further, in the plasma processing apparatus intended to decrease the adhesion of reaction products to the inner wall of the vacuum vessel or enable cleaning for the inner wall of the vacuum vessel by providing the Faraday shield between the induction antennas disposed on the outer circumference of the vacuum vessel and plasmas and connecting the RF power source to the Faraday shield to supply electric power, the range of the aimed effect is limited.

SUMMARY OF THE INVENTION

[0011] The present invention has been accomplished in view of the foregoing situations and it is an object of the present invention to provide a plasma processing apparatus of excellent mass production stability by controlling deposition films deposited on the inner wall of a vacuum vessel.

[0012] According to one aspect of the present invention, there is provided a plasma processing apparatus comprising:

[0013] a gas ring forming a portion of a vacuum processing chamber and having a blowing port for a processing gas;

[0014] a bell jar covering a portion above the gas ring to define a vacuum processing chamber;

[0015] an antenna, disposed above the bell jar, for supplying RF electric fields into the vacuum processing chamber to form plasmas;

[0016] a sample table for placing a sample in the vacuum processing chamber;

[0017] a Faraday shield disposed between the antenna and the bell jar and applied with an RF bias voltage; and

[0018] a deposition preventive plate attached-detachably to the inner surface of the gas ring excluding the blowing port for the processing gas;

[0019] wherein the area of the inner surface of the gas ring including the deposition preventive plate that can be viewed from the sample surface is set to about ½ or more of the area of the sample.

DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0020] Other objects and advantages of the invention will become apparent from the following description of embodiments with reference to the accompanying drawings in which:

[0021]FIG. 1 is a diagram of a plasma processing apparatus according to a preferred embodiment of the present invention;

[0022]FIG. 2 is a schematic perspective view of a Faraday shield;

[0023]FIG. 3 is a graph for explaining a method of optimizing FSV;

[0024]FIG. 4 is a circuit diagram for explaining FSV feedback control;

[0025]FIGS. 5A and 5B are side views showing examples of attaching the Faraday shield to the bell jar;

[0026]FIGS. 6A, 6B and 6C are diagrams for explaining attaching structures of a deposition preventive plate;

[0027]FIG. 7 is a graph showing an example of heat calculation for the deposition preventive plate;

[0028]FIG. 8 is a diagram explaining a supporting structure for the deposition preventive plate;

[0029]FIGS. 9A and 9B are views explaining a countermeasure for deposit deposited on the bell jar inner wall;

[0030]FIG. 10 is a view explaining adhesion of deposit near the deposition preventive plate;

[0031]FIG. 11 is a view showing an example of a structure of the deposition preventive plate;

[0032]FIG. 12 is a view showing another example of a structure of the deposition preventive plate;

[0033]FIG. 13 is a view showing a further example of a structure of the deposition preventive plate;

[0034]FIG. 14 is a view showing a structure of a sample holding portion including the sample table;

[0035]FIG. 15 is a diagram of a substrate bias circuit including a susceptor surface;

[0036]FIG. 16 is a graph for explaining a relation between a susceptor thickness and a bias voltage generated on the susceptor surface;

[0037]FIG. 17 is a view explaining the state of adhesion of deposit on a thin-walled susceptor;

[0038]FIG. 18 is a view explaining the state of adhesion of deposit on a thin-walled susceptor;

[0039]FIG. 19 is a view showing an example of flame spraying a metal film to the lower surface of the susceptor;

[0040]FIG. 20 is a view showing an example of flame spraying a metal film to the lower surface of the susceptor;

[0041]FIG. 21 is a view showing an example of embedding a metal film in the susceptor;

[0042]FIG. 22 is a view showing an example of embedding a metal film in the susceptor;

[0043]FIG. 23 is a view showing an example of applying a susceptor having a metal film to a sample table made of ceramic dielectrics;

[0044]FIG. 24 is a view showing an example of applying a susceptor having a metal film to a sample table made of ceramic dielectrics;

[0045]FIG. 25 is a view showing a connection structure for bias applying electrode;

[0046]FIG. 26 is a circuit diagram for explaining means for controlling an RF bias voltage applied to a susceptor surface;

[0047]FIG. 27 is a view for explaining a structural example of a means for controlling an RF bias voltage applied to a susceptor surface;

[0048]FIG. 28 is a circuit diagram for explaining an example of supplying RF bias to a susceptor by using a separate power source;

[0049]FIG. 29 is a view for explaining an example of an electrode structure in a case of supplying RF bias to a susceptor by using a separate power source;

[0050]FIG. 30 is a graph for explaining a method of optimizing a susceptor bias voltage;

[0051]FIG. 31 is a circuit diagram for explaining a susceptor bias application circuit having a feedback circuit;

[0052]FIG. 32 is a circuit diagram for explaining a susceptor bias application circuit having a feedback circuit; and

[0053]FIG. 33 is a view for explaining each of regions in the inside of a vacuum processing chamber.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0054] A first embodiment of the present invention is to be described with reference to the drawings. In the first embodiment, a method of suppressing deposition of reaction products during processing on the inner wall of a vacuum vessel is to be described with reference to an example of an etching process in a case where a sample put to plasma processing is a non-volatile material.

[0055]FIG. 1 is a cross sectional view of a plasma processing apparatus according to this embodiment. A vacuum vessel 2 has a bell jar 12 made of an insulative material (for example, non-conductive material such as quartzes or ceramics) closing an the upper portion of the vacuum vessel 2 to define a vacuum processing chamber. A sample table 5 for placing a sample 13 to be processed is provided inside the vacuum vessel and plasmas 6 are formed in the processing chamber to process the sample. Further, the sample table 5 is formed above a sample holding unit 9 including the sample table.

[0056] Coiled upper antenna 1 a and lower antenna 1 b are disposed on the outer circumference of the bell jar 12. A disk-like Faraday shield 8 put into capacitive coupling with the plasmas 6 is disposed outside the bell jar 12. The antennas 1 a and 1 b and the Faraday shield 8 are connected in series by way of a matching box to an RF power source (first RF power source) 10 as will be described later. Further, a serial resonance circuit (a variable capacitor VC3 and a reactor L2) having variable impedance is connected in parallel between the Faraday shield 8 and the ground.

[0057] A processing gas is supplied by way of a gas supply pipe 4 a to the inside of the vacuum vessel 2 and the gas in the vacuum vessel 2 is evacuated to a predetermined pressure by an exhausting device 7. The processing gas is supplied from the gas supply pipe 4 a to the inside of the vacuum vessel 2. In this state, the processing gas is converted into plasmas by the effect of electric fields generated by the antennas 1 a and 1 b. The placing electrode 5 is connected with a substrate bias power source (second RF power source) 11. This can draw ions present in the plasmas onto the sample 13.

[0058] An RF power source 10, an RF power with a HF band such as, 13.56 MHz, 27.12 MHz or 40.68 MHz, or an RF power source of higher frequency such as of VHF band is used and plasma generating electric fields can be obtained in the vacuum vessel 2 by supplying the RF power to the induction coupled antennas 1 a and 1 b and the Faraday shield 8. In this case, reflection of the electric power can be suppressed by matching the impedance of the induction coupled antennas 1 a and 1 b with the output impedance of the RF power source 10 by use of the matching box 3. Variable capacitors VC1 and VC2 connected in an inverted L-shape as shown, for example, in the figure is used as the matching box 3.

[0059] The Faraday shield is made of a conductor formed with longitudinal strip-shaped slits 14 as shown in FIG. 2 and disposed in a manner overlapping the vacuum vessel (bell jar 12) made of ceramics. The voltage applied to the Faraday shield 8 can be controlled by a variable capacitor (VC3 shown in FIG. 1) The voltage applied to the Faraday shield 8 (shield voltage) is preferably set to an optional value corresponding to the processing recipe or cleaning treatment recipe on every wafer.

[0060] The principle of the cleaning for the inner wall of the vacuum vessel by the Faraday shield is as described below. That is, a bias voltage is generated inside the vacuum vessel (inner wall of the bell jar) by an RF voltage applied to the Faraday shield, thereby drawing ions present in the plasmas toward the wall of the vacuum vessel, and bombarding the vacuum vessel wail by the drawn ions to cause physical and chemical sputtering and prevent deposition of reaction products on the wall of the vacuum vessel.

[0061] An optimal Faraday shield voltage (FSV) exists for the cleaning of the inner wall by the Faraday shield. The optimal FSV undergoes the effects of the RF power source frequency, materials for the vacuum vessel wall, plasma density, plasma composition, constitution for the entire vacuum vessel, materials for the sample to be processed, processing rate and the processing area. Accordingly, the optimal FSV value has to be changed on every process.

[0062]FIG. 3 is a graph for explaining a method of optimizing FSV, which shows a relation between FSV and a light emission intensity (light amount) of a material for the vacuum vessel wall (aluminum or oxygen constituting alumina in a case where the wall material is made of alumina). As shown in the graph, light emission of the wall material increases as the FSV is higher at a certain FSV value (point b in FIG. 3) as a boundary. This shows that at FSV lower than the point b, not only deposits are not deposited by sputtering for the deposits but also the wall material itself is sputtered as well at FSV not lower than the point b.

[0063] While the optimal FSV value is a voltage at the point b, a point a is sometimes determined as the optimal value depending on the process. For example, this is a case in which processing reaction of the workpiece or reaction in the gas phase are made different from intended conditions by the release of the wall material into the gas phase due to the sputtering to the material for the vacuum vessel wall, and the aimed process cannot be executed. That is, by setting FSV to the point a, deposition of deposits, is allowed though slightly, to the inner wall of the vacuum vessel, so that the wall material is not sputtered at all. This can prevent process troubles caused by the release of the wall material. However, it is necessary to clean the inner wall of the vacuum vessel by a process used exclusively for cleaning before substantial deposition of deposits on the inner wall of the vacuum vessel (the FSV is set higher than the point b in this case).

[0064] On the contrary, point c is sometimes set as an optimal value depending on the process. For example, aimed process can not sometimes be conducted stably when reaction products are deposited, if little, on the inner wall of the vacuum vessel, obstacles are generated or the RF power for generating the plasmas is absorbed to the deposits to vary the plasma characteristics. In this case, FSV is set to the point c as described above. That is, it is possible to set the condition such that the inner wall may be scraped somewhat but the reaction products are not deposited at all. In this case, it results in a drawback that the vacuum vessel is consumed greatly but the number of cleaning cycles for the inner wall cal be decreased.

[0065] FSV is set to the point b in a case where neither the scraping of the inner wall nor the deposition of the reaction products is desirable. In this case, it is important to improve the reproducibility for the FSV setting voltage. This is because change with the lapse of time has to be suppressed in a case of conducting the same process in different apparatus or conducting the same process continuously even in the same apparatus. For this purpose, feedback control for FSV is important.

[0066]FIG. 4 is a circuit diagram for explaining the FSV feedback control. As shown in the figure, output of the RF power source 10 for plasma generation is applied by way of the impedance box (VC1, VC2) and antennas 1 a and 1 b to the Faraday shield 8. FSV is divided by the capacitors C2 and C3 into a small signal, which is passed through a filter 15 to eliminate harmonic waves or other frequency components, detected by a detector 16, converted into a DC voltage and then amplified by an amplifier 17. Thus, a DC voltage signal in proportion with FSV is obtained. The signal is compared with a preset value or a setting value set by the recipe output of a main body apparatus control unit 20 to control a motor by way of a motor controller 19 and rotate a variable capacitor VC3 for determining the FSV voltage. Thus, FSV can be controlled to a value set by the main body apparatus control section 20. For example, the FSV value can be controlled constant also in a case of conducting the same processing in different apparatus or continuously in the same apparatus. Further, difference between the apparatus or a change with the lapse of time can be suppressed.

[0067] The Faraday shield is put to capacitive coupling with plasmas through the wall (bell jar) of the dielectric vacuum vessel. As a result, FSV is divided into static capacitance between the Faraday shield and the plasmas and static capacitance due to ionic sheath formed to the wall, and the voltage after division is applied to the ionic sheath. This accelerates the ions and causes ion sputtering to the inner wall of the vacuum vessel. For example, in a case where the thickness of the wall of the alumina vacuum vessel is 10 mm, the voltage applied to the ionic sheath is about 60 V for FSV of 500 V.

[0068] Increase of the voltage applied to the ion sheath with low FSV is useful. This is because generation of high FSV makes the handling difficult by the reason, for example, that this tends to cause abnormal discharge. In order to increase the voltage applied to the ionic sheath by low FSV, it is effective to make the static capacitance as low as possible between the Faraday shield and the plasmas since the static capacitance of the ionic sheath is determined solely by the plasma characteristics of the process. In order to attain this, it is necessary that the dielectric constant of the material of the dielectric vacuum vessel is high and the thickness of the wall of the dielectric vacuum vessel is as thin as possible. As the material suitable to this purpose, an alumina can be adopted as a typical material having high strength and high dielectric constant.

[0069] When a vacuum vessel of thin wall thickness is manufactured by a highly dielectric material such as alumina, it is necessary to consider a gap between the Faraday shield and the wall (bell jar) of the vacuum vessel. Since the dielectric constant of alumina is about 8, the wall thickness of 10 mm is: 10/8=1.25 mm when converted as the thickness of atmospheric air. Assuming a case where the gap between the Faraday shield and the vacuum vessel is 0 to 1 mm, the gap between the Faraday shield and the plasma changes nearly about one-half as 1.25 to 2.25 mm when converted as that for atmospheric air. This means that the voltage applied on the ionic sheath changes from about 33 to 60 V under the conditions described above.

[0070] When the voltage applied on the ion sheath changes greatly as described above, deposits are adhered to some portions while deposits are not deposited to other portions on the inner wall of the vacuum vessel to reduce the effect of suppressing adhesion of deposits by the application of FSV. In order to prevent this, it is necessary to make the gap between the Faraday shield and the vacuum vessel constant or to prepare a Faraday shield with a thin film and put it into intimate contact with the vacuum vessel.

[0071] While it is easy to manufacture the Faraday shield by fabrication of a metal plate, it is not practical to manufacture such that the gap relative to the wall (bell jar) of the vacuum vessel is 0.5 mm or less. However, the gap between the Faraday shield and the vacuum vessel can be filled by attaching a conductive elastomeric material, for example, a conductive sponge to a portion below the Faraday shield.

[0072]FIGS. 5A and 5B are views showing an example of attaching a Faraday shield to a bell jar. FIG. 5A shows an example where a gap is present between the Faraday shield 14 and the bell jar 12, in which deposits are tend to deposit on the inner surface of a vacuum vessel at a portion with gap. On the other hand, deposits are not deposited near a skirt portion with no gap. FIG. 5B is a view showing an example where the gap is filled with an elastomeric conductor 12 a, for example, conductive sponge. This can provide the Faraday shield 14 with the same effect as that it is in close contact with the bell jar 12. Since the conductive sponge is highly shrinkable, it can bury gaps of different sizes flexibly.

[0073]FIGS. 6A and 6B are views explaining an attaching structure of a deposition preventive plate. FIG. 6A shows a gas blowing port 23 formed at a skirt portion of the bell jar 12 and a gas ring thereblow. In the constitution, when plasma processing is continued, deposits are deposited at the portions indicated by A and B of the figure. The deposits can be prevented from deposition on the inside of the bell jar at a portion above B in the figure by the ion sputtering effect of FSV. A consideration has to be taken for the portions A and B. The portion A is the periphery of the gas blowing port 23 and, when deposits are adhered there, the deposits are liable to peel off by the effect of the gas stream, and the peeled deposits are placed as obstacles on the wafer as a workpiece to hinder the process. Further, the portion B is the inner wall of the bell jar 12 but the Faraday shield 14 is far from the inner wall of the bell jar. Accordingly, the ionic sheath voltage due to FSV is lowered and the effect of suppressing the adhesion of the deposits by ion sputtering is not so effective for the portion B.

[0074]FIG. 6B is a view for explaining a structure covering the gas blowing port 23 with a deposition preventive plate 22. The portion A is the periphery of the gas blowing port and adhesion of the deposits to the portion has to be decreased as much as possible. In order to decrease the adhesion of deposits to the gas blowing port 23, it is necessary to decrease the region of the plasmas 6 which can be seen from the gas blowing port 23 through the hole of the deposition preventive plate 22, that is, to decrease the view angle relative to the plasmas, and it is also necessary that the gas blowing port 23 does not directly view the wafer, that is, the central axis of the gas blowing port 23 is set in the direction of the plasma forming space above the sample such that the sample is contained in a region out of the view angle.

[0075]FIG. 6C is a view showing a detailed example of a relation between the deposition preventive plate and the gas blowing port. In this example, the view angle is decreased to about 30° and the wafer cannot be viewed directly through the gas blowing port.

[0076] It is effective to make a gap between the deposition preventive plate 22 and the gas jetting port 23. The size of the gap is preferably 0.5 mm or more. The gap provides several advantageous. At first, even with the hole of the same size formed in the deposition preventive plate for passing the gas, the view angle to the plasmas can be made smaller by providing the gap and the amount of deposits adhered to the gas blowing port 23 can be decreased. Further, when a gas is blown from the gas jetting port 23 into the vacuum vessel, a large lowering of pressure occurs and the gas is formed from a viscous flow into a intermediate flow and finally formed into a molecular stream. In this case, at the periphery of the gas glowing port 23, the pressure of the gas is still relatively high and the gas is in a state of the intermediate flow and, the deposits adhered at the periphery of the port undergoes the effect from the gas stream tending to be peeled. By the provision of the gap, the gas flow near the deposition preventive plate 22 is formed into the molecular stream and the gas stream has less effect of peeling the deposits adhered on the deposition preventive plate to decrease the peeling of the deposits. Further, as will be described later, the temperature of the deposition preventive plate 22 can be elevated efficiently to decrease the amount of deposits adhered to the deposition preventive plate 22.

[0077]FIG. 7 is a graph showing an example of heat calculation of the deposition preventive plate. The result of process has provided a finding that a material such as Fe or Pt is less adhered to a member at a temperature of 250° C. or higher. Then, the deposition preventive plate was designed such that the temperature of the deposition preventive plate is 250° C. or higher. In the heat design, heat balance was calculated for the input heat from the plasmas, heat dissipation from the supporting portion or the deposition preventive plate and the dissipation of radiation heat from the entire deposition preventive plates. FIG. 7 shows the result of the heat calculation.

[0078] In a case of a deposition preventing plate made of SUS (stainless steel), it can be seen that the equilibrium temperature exceeds 250° C. at RF input to plasmas of about 500 W. In a case of a deposition preventive plate made of Al (alumite finished surface), the equilibrium temperature of the deposition preventive plate is 250° C. or higher at an RF input of 1000 W. The structural features for each of the portions are to be described upon calculation.

[0079] Since plasma input heat is diffused isometrically in a reactor, it is calculated as RF input plasma x area of deposition preventive plate/entire plasma contact area. In the deposition preventive plate designed now, input heat to the deposition preventive plate is 260 W at a RF input to plasmas of 1200 W.

[0080] The dissipation of heat irradiation from the deposition preventive plate can be suppressed low since the surface radiation rate can be decreased to about 0.2 by applying mirror finishing to the surface. In a case of using Al (alumite finished surface) for the deposition preventive plate, the diffusion of heat radiation is somewhat increased since the radiation ratio of the alumite surface is about 0.6.

[0081]FIG. 8 is a diagram for explaining a supporting structure of the deposition preventive plate. The heat conduction surface is decreased by supporting the deposition preventive plate for the entire circumference at three points so as to decrease the heat transfer from the supporting portion and bringing the area of contact with the gas ring main body into a substantially point-to-point contact. In a concrete example, the radial length for the portion of contact is defined as 3 mm and the circumferential length for the portion of contact is defined as 1 mm. Even when the contact heat resistance is assumed to an excess value of about 3000 [W/(m²·K)], heat transfer from the supporting portion of the deposition preventive plate calculated according to: area of contact×contact heat transmission ration×(temperature at the inner surface of deposition preventive plate−temperature of gas ring) is only about 10 W.

[0082] A deposition preventive plate was actually manufactured trially to measure the surface temperature actually. The material of the deposition preventive plate used is Al (alumite finished surface). At an RF input of 1200 W, it was confirmed that the surface temperature was about 250° C. which was substantially the designed value.

[0083] As described above, adhesion of the deposits can not be eliminated completely even when the deposition preventive plate is kept at a high temperature. Therefore, it is important to stably adhere the deposits adhered to the deposition preventive plate. For this purpose, it is desirable that the surface of the deposition preventive plate has unevenness to some extent in order to mechanically improve the adhesion of the deposits. According to the experiment made by the inventors, it has been found that the surface roughness is preferably 10 μm or more.

[0084] However, when adhesion of the deposits is started, the thickness of the adhered deposits is gradually increased from the thin film state. For example, unevenness of 10 μm formed in the deposition preventive plate has an anchoring effect for deposits with a film thickness of about 10 μm. However, as the thickness of the adhered deposits increases, the anchoring effect is reduced. Accordingly, in order to effectively provide the anchoring effect from the initial state where the adhesion amount of the deposits is small to a state where the amount of the deposits increases to some extent, it is preferred that two types of unevenness for example, 10 μm unevenness and 100 μm unevenness are formed simultaneously on the surface. The fabrication method for forming such unevenness includes knurling for the formation of 100 μm unevenness and blasting fabrication for formation of 10 μm unevenness.

[0085] As has been described above, in order to elevate the temperature of the deposition preventive plate, it is preferred to apply mirror finishing to the surface of the deposition preventive plate and apply unevenness formation to the surface for stably adhering the deposits. Accordingly, in practice, unevenness can be formed, in the deposition preventive plate, on the surface where the deposits are adhered (plasma facing surface) and mirror finishing can be applied to the surface not adhered with the deposits (for example, surface facing the gap between the deposition preventive plate and the gas blowing port). Further, to reflect heat irradiated from the deposition preventive plate, mirror finishing is preferably applied to the surface of the portion not adhered with the deposits in the surface of the gas ring with the gas blowing port.

[0086] The size of the deposition preventive plate is preferably a minimum size capable of covering the gas blowing port. This is because deposition of the deposits to some extent on the deposition preventive plates is inevitable and thermal hysteresis is caused in the deposition preventive plate in view of elevating the temperature to decrease the adhesion amount of the deposits, and the deposits are liable to peel off due to the difference between the thermal expansion and shrinking amounts of the deposits and the deposition preventive plate material.

[0087] Further, the deposition preventive plate is preferably manufactured with an electroconductive material and it is preferably grounded to the earth. This is because electric discharge is stabilized as the grounding area relative to the radio frequency waves for the generation of plasmas is increased. Further, since the deposits are liable to peel off due to the repulsion between the deposits by the coulomb effect when the deposits are electrostatically charged, and this is provided for the purpose of preventing electrostatic charging on the deposits as much as possible.

[0088] The structural design and the heat design described above were conducted, a deposition preventive plate with the surface roughness of 10 μm and 100 μm was manufactured and platinum Pt was continuously etched for 500 sheets to examine the performance. As a result, adhesion of the deposits to the gas blowing port was scarcely observed. Further, deposits adhered to the deposition preventive plate were stable and peeling of the deposits did not occur.

[0089]FIGS. 9A and 9B are views for explaining the countermeasure for the deposits adhered to the portion B in FIG. 6A (the portion on the inner wall of the bell jar 12 where the Faraday shield is far from the inner wall of the bell jar and accordingly, a portion where the ionic sheath voltage by FSV is lowered and the effect of suppressing the adherance of deposits by the ion sputtering does not exert effectively).

[0090] The portion B in FIG. 6A is a region where the ion sputter by FSV is less effective since the distance between the inner wall of the bell jar 12 and the Faraday shield 14 is large. Then, when the deposition preventive plate 2 is extended to cover the portion, the adhesion amount of the deposits can be decreased and the deposits can be stabilized. FIG. 9A shows the structure. When a test was conducted on the adhesion of deposits by using the structure, it was found that deposits were adhered to a region of about 15 mm in width of the bell jar of the inner wall around point C in FIG. 9A as a center.

[0091]FIG. 9B is a modified example of FIG. 9A. As shown in the figure, the bell jar 12 is formed such that the inner surface thereof is substantially in contiguous with the inner surface of the gas ring 4 and the bell jar 12 was disposed on the gas ring 4 to form the vacuum processing chamber.

[0092] With this constitution, the deposition preventive plates can be formed continuously with the inner surface of the bell jar and the inner surface of the gas ring. Thus, the region where the ion sputtering by FSV is less effective can be protected effectively by the deposition preventive plate.

[0093]FIG. 10 is a view for explaining adhesion of deposits near the deposition preventive plate. At first, a dotted line shows an equi-density line of plasmas. Referring to the point ° C., the point C corresponds to a corner for the deposition preventive plate and the bell jar and the density of plasmas is slightly lower at the portion compared with that for the periphery.

[0094] This is because plasmas are less turned behind the point C due to the thickness of the deposition preventive plate. Accordingly, it is probable that the deposits are less detached since the number of ion sputtering per unit area on the inner wall of the bell jar is smaller at the point C. There may be another reason. This is, because the deposition preventive plate is electroconductive and FSV is not effective to the ionic sheath formed in the deposition preventive plate and a DC voltage of about 15 to 20 V determined by plasma characteristics is applied to the ion sheath. On the contrary, in a region where FSV is effective, an RF voltage, for example, of about 60-V is further applied in addition to the DC voltage determined by the plasma characteristics onto the ionic sheath formed on an inner wall of the bell jar, which effectively accelerates ions to sputter the inner wall of the bell jar. That is, the periphery of the point C corresponds to a transition region from the ionic sheath at a low voltage formed in the deposition preventive plate to the ionic sheath at high voltage formed in the inner wall of the bell jar, and the periphery for the point C is a region where the ionic sheath voltage is increased and the ion sputtering becomes more effective gradually as it aparts form the vicinity of the deposition preventive plate.

[0095] It is probable that a weak sputter, region by FSV is formed near the point C as shown in FIG. 10 by the two reasons described above. It is probable that the deposits are adhered in the region since adhesion of the deposits is predominant over the sputtering by FSV.

[0096]FIGS. 11, 12 and 13 are views showing, respectively, structural examples of the deposition preventive plates. As shown in FIG. 11, a knife edge-shaped deposition preventive plate was manufactured in order to remove the cause for the lowering of the plasma density which is one of the reason of forming the weak sputter region and a test was conducted. As a result, as shown in FIG. 11, it was confirmed that the weak sputter region is contracted and the deposit adhesion region is contracted. Then, to remove another cause, when an upper portion 22 a of the deposition preventive plate is changed to an insulator (alumina in this case), the strong sputter region and the deposition region can be allowed to coincide with each other with scarce adhesion of the deposits as shown in FIG. 12. Since knurling is impossible for the surface of alumina, unevenness was fabricated on the surface by a blast treatment. Further, for the material of the insulator, quartz or aluminum nitride can also be used.

[0097] To further prevent adhesion of deposits more thoroughly, it may suffice that the strong sputter region is wider, even slightly, than the deposit adhesion region as shown in FIG. 13. Then, a gap was made between the deposition preventive plate and the bell jar such that plasmas could intrude between the deposition preventive plate and the bell jar. To allow entrance of plasmas, it is necessary that the distance of the gap be substantially lager than the ionic sheath and be 5 mm or more. On the contrary, if it is excessively large, since the deposits turned behind by diffusion, the effect is reduced. Since the maximum value for the gap to inhibit the deposits from being turned behind by the diffusion is determined depending on the material of the deposits, and species and pressure of gas, it is about 15 mm as a result of a test while it is different depending on the processing process. As a result of manufacturing a deposition preventive plate of the structure shown in FIG. 13 and conducting a test, adhesion of deposits to the bell jar could completely be suppressed. In this structure, it is not necessary that the upper portion of the deposition preventive plate is an insulative material but the same performance can be obtained even when it is made of an electroconductive material.

[0098] An upper portion of the susceptor as a cover for the sample table 5 also causes obstacles formed on the wafer when the deposits are adhered. Then, an RF bias was applied also to the susceptor to cause physical and chemical ion sputtering, so that the deposits were not adhered.

[0099]FIG. 14 is a view showing a structure of a sample holding portion 9 including a sample table. As shown in the drawing, the sample table 5 connected with a substrate bias voltage 11 is mounted on a ground base 36 and an insulation base 35. As the material for the sample table, aluminum or titanium alloy is used generally. A dielectric film is formed in an upper portion of the sample table but at a portion for mounting a workpiece (sample 13) such that the workpiece can be electrostatically attracted. While the dielectric film is made of a flame sprayed film in the drawing, it is sometimes formed of a polymeric material such as epoxy, polyimide or silicone rubber. Further, the ceramic materials formed, for example, by flame spraying can include alumina, alumina nitride, and PBN (Pyrolitic Boron Nitride). Further, FIG. 14 shows a structure of providing shielding using the ground base 36 and the insulation cover 37 in order that the RF power passes through the lateral side of the sample table 5 to the plasmas. Further, the susceptor is generally made of a material such as quartz or alumina so that it covers an electrode portion of the sample table except for the surface where the sample is mounted, to prevent plasma-induced injury.

[0100]FIG. 15 is a view showing a substrate bias circuit (equivalent circuit) including a surface of the susceptor. The output from the substrate bias power source 11 is mixed with a DC voltage for electrostatic attraction supplied from an electrostatic attraction power source in an impedance matching box (MB) 32 and then supplied to the sample table 5. In this case, radio frequency waves from the substrate bias power source 11 are supplied also to the upper surface of the susceptor while passing from the sample table 5 to the susceptor 34. The susceptor 34 forms in this embodiment a capacitor using the susceptor material as a dielectric material. The thus formed capacitor is represented as a capacitor C (33) in FIG. 15.

[0101] The present inventors, at first, experimentally examined adhesion of the deposits when the susceptor thickness was set to 5 mm as shown in FIG. 14. As a result, it has been found that a great amount of deposits was adhered on the upper surface of the susceptor.

[0102] Then, the relation between the thickness of the susceptor 34 and the bias voltage formed on the surface of the susceptor was theoretically examined. The result is shown in FIG. 16. It is known that adhesion of deposits can be suppressed when the voltage formed on the bell jar inner wall is about 60 V or more. Further, according to the test conducted by the inventors, since the bias voltage (peak-to-peak) Vpp was often set in a range about from 400 to 500 V in the test, the susceptor was selected to have a thickness of 4 mm so that a voltage of 60 V or higher could be generated on the surface of the susceptor within the range of the bias voltage Vpp.

[0103]FIGS. 17 and 18 are views for explaining the adhesion state of deposits to the susceptor of a thin-wall thickness (for example, 4 mm thickness). As shown in FIG. 17, the deposits was experimented for the adhesion state thereof with the entire thickness of the upper surface of the susceptor being set to 4 mm. As a result, it was confirmed that deposits were not adhered in a range shown by arrows in the drawing (deposition restriction region). Thus, it was found that adhesion of the deposits could be suppressed for the portion in direct contact with the sample table. However, in the constitution of FIG. 17, since deposits are adhered to the outer circumference of the upper surface of the susceptor, they may hinder the processing as obstacles to the workpiece. Then, the insulation cover 37 disposed on the side of the sample table was removed so that the sample table and the susceptor were in contact with each other entirely for the upper surface of the susceptor and the upper portion of the side of the susceptor. The constitution is shown in FIG. 18. The adhesion state of the deposits was examined experimentally in the same manner as above by using the structure shown in FIG. 18. As a result, deposits were not adhered on the upper surface of the susceptor and the upper portion for the side of the susceptor in contact with the sample table. However, it was found that when the susceptor was attached and detached repeatedly, the deposits could not be removed sufficiently even under the same condition. Further, it was found that when the deposits were not removed completely, the deposits were deposited with a localized distribution and, the deposits tended to remain on the surface of the susceptor particularly.

[0104] The reason why the deposits were deposited with the localized distribution and the deposits could not be removed sufficiently was estimated as below. That is, since the susceptor is made of alumina, the thickness is 4 mm, and the dielectric constant is about 8, it corresponds to about 0.5 mm when converted as an air layer. Assuming the gap as 0.1 mm between the susceptor and the sample table for example, the thickness of the dielectric material forming the capacitor C in FIG. 15 is a total of 0.5 mm for the susceptor and 0.1 mm for the gap, which varies in the range from 0.5 to 0.6 mm (20%). The variation causes localization of the RF voltage generated on the surface of the susceptor to cause localization in the removal of the deposits. However, it is difficult and not practical to manufacture the susceptor and the sample table such that they are in close contact with an accuracy of the gap of 0.1 mm or less.

[0105] In order to overcome the problem, as shown in FIG. 19, a flame sprayed metal film 39 was formed by flame spraying a metal film to the lower surface of a susceptor 34. Tungsten was used for the flame sprayed metal because it was known that tungsten has good bondability with alumina. The metal film is not necessarily tungsten so long as the film has an electroconductivity and good bondability with the susceptor, and gold, silver, aluminum or copper may also be used. Further, the preparation method for the metal film is not necessarily restricted to the flame spraying but any of methods capable of forming a thin film such as plating, sputtering, vapor deposition, printing, coating and adhesion of thin film may also be used. When this structure is adopted, since the same voltage as that for the sample table is generated for the entire metal film so long as the metal film and the sample table 5 are in contact with each other at one position, the problem caused by the gap between the susceptor and the sample table can be avoided.

[0106] As a result of examining the adhesion state of the deposits by an experiment using the apparatus of the constitution shown in FIG. 19, adhesion of deposits in the deposition restriction region for the deposits shown by arrows could be eliminated with good reproducibility. The advantage of this method is that the same voltage as that for the sample table 5 is generated over the entire metal film so long as the metal film and the sample table are in contact with each other even at least at one point to generate a uniform RF voltage on the surface of the susceptor 34. Accordingly, as shown in FIG. 20, even in a state where other structures such as the insulation cover 37 are present, a uniform RF voltage can be generated on the surface of the susceptor for any range by extending the flame spraying range of the flame sprayed metal film. In the constitution in FIG. 20, it was experimentally confirmed that adhesion of the deposits could be eliminated with good reproducibility in the deposition restriction region for deposits shown by arrows.

[0107] From the results described above, it has been found that the RF voltage can be generated uniformly on the surface of the susceptor to make the restriction for the adhesion of the deposits uniform by using the metal film as formed by flame spraying. By the use of the technique, also in a case where the thickness of the susceptor has to be increased in view of the structure, the same effect can be obtained by embedding the metal film in the susceptor. FIGS. 21 and 22 show the structure.

[0108] As shown in the drawings, a flame sprayed metal film 39 is embedded at a position of a predetermined depth from the surface of the susceptor 34 (about 4 mm in the drawing), a contact is led from the flame sprayed metal film 39 to the sample table 5 to ensure the electric conduction, and the same RF voltage as that for the sample table 5 is generated to the flame sprayed metal film 39.

[0109] The sample table for placing the sample 13 can include, in addition to those types of forming electrostatic attraction film on the metal sample table, for example, by flame spraying, those types of embedding a metal electrode into the sample table made of ceramic dielectrics such as aluminum nitride or alumina, and conducting electrostatic attraction or applying RF bias by the metal electrode. Also in the case of the substrate of this type, it is possible to manufacture a susceptor having the quite same function by forming the metal film to the susceptor.

[0110]FIGS. 23 and 24 show the example described above. FIG. 23 show a case of forming a metal film to the rear face of the susceptor 34. An electrostatically attracting and RF bias applying electrode 40 made of tungsten is embedded in the sample table 5 made of aluminum nitride. A conduction patterns (flange conduction patterns 41, 42, 43) are embedded from the electrode to the flame sprayed metal film 39 to make electric conduction between the electrode 40 and the flame sprayed film 39. This can generate the same RF voltage as that for the tungsten electrode to the flame sprayed metal film 39 at the rear face of the susceptor. Naturally, the deposition restriction performance of the deposits to the surface of the susceptor by the structure is the quite same as that described previously.

[0111]FIG. 24 is an example of embedding a flame sprayed metal film 39 in the inside of a susceptor 34, in which quite the same effect can be provided in function as in the embodiment of FIG. 23 by extending the conduction patterns described for FIG. 23 (flange conduction patterns 41, 42, 43) and connecting the electrode 40 embedded in the sample table 5 to the flame sprayed metal film 39 embedded in the susceptor 34 by contact.

[0112] In the case of the placing electrode 5 shown in FIG. 23 or FIG. 24, it is necessary to prepare a pattern for supplying radio frequency waves from the electrostatically attracting and RF bias applying electrode 40 embedded in the electrode 5 to the flame sprayed metal film 39, and FIG. 25 shows such an example.

[0113] In FIG. 25, a flange conduction pattern 41 in parallel with the electrostatically attracting and RF bias applying electrode 40 made of tungsten is formed by embedding a tungsten thin film like the tungsten electrode in the placing electrode. The embedded tungsten thin films can be connected with each other by a method of extending through a hole at a necessary portion after forming the placing electrode and brazing a perforation terminal.

[0114] With the bias application method to the susceptor described so far, adhesion of deposits on the upper surface of the susceptor are just suppressed when the RF voltage for the sample table is at a certain value (400 V in this embodiment). However, if the voltage for the sample table is higher, the RF voltage on the surface of the susceptor is increased excessively to result in a problem that susceptor is scraped to shorten the part life. This drawback can be overcome as shown in FIG. 26 by using means for controlling the RF bias voltage applied to the surface of the susceptor from the outside. FIG. 26 shows a circuit for controlling the voltage for the susceptor metal film by a variable capacitor VC attached externally. FIG. 27 is an actual structure thereof.

[0115] A ceramic cover 50 is formed, for example, by flame spraying on the surface of the sample table at a portion in contact with the susceptor such that the susceptor flame sprayed metal film 51 and the sample table 5 are not in direct contact with each other. The ceramic cover 50 has a function of forming a capacitor C′ shown in FIG. 26 and transmitting a portion of the RF voltage applied to the sample table 5 to the susceptor flame sprayed metal film 51. Then, the RF voltage applied to the sample table 5 is transmitted to the susceptor flame sprayed metal film 51 by another external variable capacitor VC. Since the RF voltages transmitted by the two capacitors are at the same phase, they are simply added, and an RF voltage generated on the surface of the susceptor is determined depending on the voltage. For example, assuming the susceptor thickness as 4 mm, the surface area of the susceptor flame sprayed metal film as 400 cm², the thickness of the ceramic cover made of alumina as 300 μm and the maximum capacitance of the variable capacitor VC as 8000 pF, the voltage on the surface of the susceptor is variable within a range from about 30 to 100 V by varying the capacitance of the variable capacitor VC at a bias RF voltage of the sample table of 400 V. As described above, proper selection of the susceptor thickness, the ceramic cover, the surface area of the flame sprayed metal film and the variable capacitor VC allows to control the RF voltage generated on the surface of the susceptor. Further, although not illustrated, the susceptor flame sprayed metal film may also be incorporated in the inside of the susceptor so long as this can be connected with the variable capacitor VC.

[0116] It is also possible to make the bias voltage applied to the susceptor variable also by using a separate RF power source from the RF power source for supplying an RF power to the sample table, which is shown in FIG. 28. In this embodiment, a susceptor bias power source 11 a for supplying the RF power to the susceptor metal film is used separately from the substrate bias power source 11 for supplying bias to the sample table. FIG. 29 shows an electrode structure in this case. It is important that insulation and grounding shield (grounding base 36) are incorporated between the sample table 5 and the susceptor flame sprayed metal film 51 such that the RF voltage applied to the susceptor flame sprayed metal film 51 undergoes no effect by the RF voltage. With this constitution, although there is a drawback of requiring the susceptor bias power source 11 a, the bias applied to the susceptor can be controlled quite independently of the RF voltage applied to the sample 13. Further, the susceptor flame sprayed metal film 51 in this embodiment can be incorporated into the inside of the susceptor although not illustrated so long as it can be connected with the susceptor bias power source 11 a.

[0117]FIG. 30 is a graph for explaining the method of optimizing the susceptor bias voltage. Like FSV described previously, there also exists an optimal value for the susceptor bias voltage. The voltage is influenced by the frequency of the bias power source, material and the thickness of the susceptor, plasma density, plasma composition, constitution for the entire vacuum reactor, and the material, processing rate and processing area of the sample. Accordingly, the optimal voltage of the susceptor bias voltage has to be changed for every process. Similarly to the embodiment in FIG. 3, light emission from the susceptor material is increased as the susceptor bias voltage is higher at a certain value of the susceptor bias voltage (point b in FIG. 3) as a boundary. It shows that the susceptor bias voltage at the point b or lower is associated with the state where deposits are deposited on the susceptor, while the susceptor bias voltage at the point b or higher is associated with the state where the deposits are sputtered and not deposited, as well as the susceptor material itself is sputtered.

[0118] While the optimal voltage for the susceptor bias voltage is at the point b, a point a is sometimes determined as the optimal value depending on the process. For example, this corresponds to a case in which processing reaction for the workpiece or reaction in the gas phase is made different from intended conditions by the release of the material into the gas phase by the sputtering to the material for the susceptor, and the aimed process can not be executed. That is, by setting the susceptor bias voltage to the point a, deposition of deposits is allowed, though slightly, to the susceptor material, by which the susceptor material is not sputtered at all. This can prevent process troubles caused by the release of the susceptor material. Instead, it is necessary to conduct cleaning for the susceptor by a process used exclusively for cleaning (in which the susceptor bias voltage is set higher than the point b) before substantial deposition of deposits on the susceptor.

[0119] On the contrary, aimed process can not sometimes be conducted stably when deposits are deposited, if little, on the susceptor due to the reason such as generation of obstacles or the like. In this case, the optimal susceptor bias voltage is set to the point c, and the condition can be set such that the susceptor may be scraped to some extent but the reaction products are not deposited at all. In this case, it results in a drawback that the susceptor is consumed greatly but can provide an advantage that cleaning for the susceptor can be decreased.

[0120] On the contrary, there is a case where aimed process can not be conducted stably when the deposits are adhered, even little, on the susceptor by the reason such as occurrence of obstacles and the like. In this case, it is possible to set the optimal point of the susceptor bias voltage to point c and set to such conditions that the susceptor may be allowed to be scraped somewhat but deposits are not deposited at all. In this case, a drawback of increasing the susceptor consumption is present but it can provide a merit capable of reducing susceptor cleaning.

[0121] The susceptor bias voltage is set to the point b in a case neither the scraping of the susceptor nor the adhesion of the reaction products is desirable. In this case, it is important to improve the reproducibility for the bias setting voltage of the susceptor. This is because change with lapse of time has to be suppressed in a case of conducting the same process in different apparatus or conducting the same process continuously even in the same apparatus. For this purpose, feedback control for the susceptor bias voltage is important.

[0122]FIGS. 31 and 32 show susceptor bias application circuits each with a feed back control circuit corresponding, respectively, to FIGS. 26 to 28. In both of the circuits, the voltage for the susceptor flame sprayed metal film is detected by way of an attenuator and filter 52 and then converted into a dc voltage. Thus, a DC voltage signal is in proportion to the susceptor bias voltage. The signal is compared with a preset value set by the recipe of the main body apparatus control section 57 or the setting value to control a motor for rotating a variable capacitor VC that determines the susceptor bias voltage in the case of FIG. 31. Further, the output of the susceptor bias power source 11 a is controlled in the case of FIG. 32. By using the method, the susceptor bias voltage can be controlled to a value set in the main body apparatus, and the value of the susceptor bias voltage can be controlled at a constant level in a case of processing by the same process in different apparatus or in the same apparatus continuously, to suppress the difference between the apparatuses and the change with time.

[0123] Methods and structures for the region to control such that the deposits are not deposited or adhered, that is, the bell jar 12, the gas blowing port 23 and the susceptor 34 have been described above. So long as the reaction products from the sample 13 or the materials synthesized in the gas phase are volatile ingredient of high vapor pressure, the materials are exhausted by the exhaustion device from the discharging portion or the periphery of the materials to be processed and most of them are exhausted although deposited to some extant to a lower portion of the electrode or the exhaustion dust.

[0124] However, when highly depositing materials, that is, materials having a low vapor pressure and adhesion coefficient to solid of about 1 (almost captured when in contact with solid) are formed as reaction products from the sample or synthesized in the gas phase, the materials are deposited on the bell jar, susceptor disposed at the periphery of the sample or vacuum reactor wall including the gas blowing port and are scarcely exhausted.

[0125] In the situation described above, when it is controlled such that the deposits are not adhered to any portion in the vacuum reactor, such highly depositing materials have no place for deposition. Accordingly, the density of the highly depositing material in the gas phase is increased to increase depositing motive force and, as a result, they are compulsorily deposited on the bell jar or the susceptor.

[0126] That is, such control not to adhere the deposits on the bell jar or the susceptor can be attained by providing a place for depositing the great amount of deposits. Then, by increasing the amount of the deposits that can be deposited, or rapidly depositing them from the gas phase, performance for controlling the amount of deposits on the bell jar or the susceptor can be enhanced.

[0127] That is, it is necessary to provide a region for depositing deposits rapidly and in a great amount from the gas phase (deposition trap region) near the periphery of the workpiece where highly depositing reaction products are formed, or periphery of plasma regions. The deposition preventive plate functions as a cover for suppressing the adhesion of deposits to the gas blowing port, since it is premise that deposits are deposited to the preventive plate itself, this is also a sort of traps.

[0128]FIG. 33 shows the inside of a vacuum reactor being divided into regions including deposits trap. At first, the bell jar region and the wafer (sample)/susceptor region are regions controlled so as not to adhere deposits. All other regions in contact with the plasmas are deposition trap regions, in which deposition trap region {circle over (1)} is a region including the deposition preventive plate and a lower portion of the gar ring. The region {circle over (1)} can be directly observed (viewed) from the wafer. The bell jar region, the wafer/susceptor region and the deposition trap region {circle over (1)} constitute all the region that can be observed (viewed) directly from the wafer, which are regions for generating plasmas and also regions where or highly depositing materials formed from the wafer in plasma gas phase are most likely to adhere. When the deposits are deposited in the regions under not controlled state, they cause obstacles to the wafer or vary the plasmas with time. Accordingly, in the region that can be observed directly from the wafer, adhesion of the deposits have to be controlled as completely as possible.

[0129] In accordance with the invention, in a case of using the structure shown in FIGS. 12 and 13 for the deposition preventive plate, 100% of the regions that can be observed from the wafer are in the deposition-controlled state. Further, also in a case of using the structures shown in FIG. 6, FIG. 9, FIG. 11, it is necessary that 90% or more of the surface area of the regions that can be observed from the wafer is in the deposition-controlled state.

[0130] Further, since the suppressing function of the bell jar region or the wafer/susceptor region can be enhanced when the deposition trap region provides a sufficient function as described above, it is preferred that the surface areas for the bell jar region and the susceptor region are as small as possible and the surface area for the deposition trap region {circle over (1)} is as large as possible. In a case where highly depositing reaction products are formed from the wafer, it has been found by the experiment conducted by the inventors that the deposition suppressing function in the bell jar region and the wafer/susceptor region is lowered when the surface area S1 for the deposition trap region {circle over (1)} is defined as: S1<0.55 SW (where SW is a wafer surface area). Accordingly, to rapidly deposit the reaction products to the deposition trap, a relation is defined as: S1≧0.5 S1 and, preferably, as: S1≧S1.

[0131] The deposition trap region {circle over (2)} is referred to as a ring cover which is present below the deposition trap region {circle over (1)}. While the region can not be observed directly from the wafer, highly depositing materials are transported through diffusion and a great amount of deposits are adhered on the upper surface thereof. The deposition trap region {circle over (3)} is a side cover for the electrode which can neither be observed directly from the wafer, but a great amount of deposits are adhered to the upper portion thereof like the deposition trap region {circle over (2)}. Since the deposition trap regions {circle over (2)} and {circle over (3)} are not directly observed from the wafer, there is less possibility that the deposits adhered thereto form obstacles to the wafer or cause change with time of plasmas. However, the deposition traps are important in order to conduct cleaning operation efficiently when the apparatus is opened to atmospheric air. That is, since the reaction products are highly depositing, 90% or more of them can be adhered and recovered in the deposition trap regions {circle over (1)}, {circle over (2)} and {circle over (3)}. Accordingly, the inside of the vacuum reactor can be cleaned efficiently by arranging the deposition trap regions {circle over (1)}, {circle over (2)} and {circle over (3)} each into a swap kit (made exchangeable) and entirely replacing them with already cleaned parts after opening to the atmospheric air. For this purpose, there are two necessary conditions that the deposit trap is light in weight and easy to be detached/attached. To make the weight of the trap reduced, it is important that the material for the deposition trap is made of a light weight material, for example, aluminum

[0132] After opening to an atmospheric air, the deposition traps are detached successively in the order of {circle over (1)}, {circle over (2)} and {circle over (3)} from the vacuum reactor and a minimal required cleaning operation is conducted. The minimal required cleaning place is, for example, the periphery of the opening for wafer transportation. Then, swap kits for deposition traps after cleaning are attached in the order opposite to the above and the evacuation can be conducted immediately. As a result, the cleaning operation can be performed at a minimal time. The cleaning operation in the procedures described above can not only shorten the cleaning time but also shorten the time required for evacuation. This is because moistures in the atmospheric air adsorbed to parts in the non-vacuum state can be minimized by opening the reactor to the atmospheric air only for the minimal required time, and the amount of the solvent remaining in the vacuum reactor can be minimized by using a cleaning solvent (pure water or alcohol) by a minimal required amount. After cleaning, the detached deposition traps {circle over (1)}, {circle over (2)} and {circle over (3)} are cleaned and then utilized again as the swap kits for atmospheric opening/cleaning operation in the next time. The regions to be arranged into the swap kits as the deposition traps are not necessarily be restricted only to the regions shown in FIG. 33. While differing depending on the process or the material to be handled, it is effective to make the entire regions to be adhered with deposits as the deposition traps. For example, in a case where deposits are adhered only in one-half or more of the region for the electrode cover, the upper-half of the electrode cover is arranged into the swap kit. On the contrary, under the conditions where the deposits are adhered as far as the exhaustion duct, it is effective to also arrange the inner wall of the exhaustion duct as the deposition trap region and arrange the same into the swap kit.

[0133] As has been described above according to the present invention, since the deposited films deposited on the inner wall of the vacuum reactor are controlled, it can provide a plasma processing apparatus and a plasma processing method of satisfactory mass production stability.

[0134] While the invention has been described in its preferred embodiments, it is to be understood that the words which have been used are words of description rather than limitation and that changes within the purview of the appended claims may be made without departing from the true scope and spirit of the invention in its broader aspects. 

What is claimed is:
 1. A plasma processing apparatus comprising: a gas ring forming a portion of a vacuum processing chamber and having a blowing port for a processing gas; a bell jar covering a portion above the gas ring to define a vacuum processing chamber; an antenna, disposed above the bell jar, for supplying a RF electric field into the vacuum processing chamber to form plasmas; a sample table for placing a sample in the vacuum processing chamber; a Faraday shield disposed between the antenna and the bell jar and applied with an RF bias voltage; and a deposition preventive plate attached detachably to the inner surface of the gas ring excluding the blowing port for the processing gas; wherein an area of the inner surface of the gas ring including the deposition preventive plate that can be viewed from the sample surface is set to about ½ or more of the area of the sample.
 2. A plasma processing apparatus as defined in claim 1, wherein the deposition preventive plate has an opening for allowing the processing gas introduced from the blowing port to pass therethrough, and the opening is opened at a view angle of about 30° at the blowing port of the processing gas.
 3. A plasma processing apparatus as defined in claim 1, wherein the deposition preventive plate is disposed at a portion, of the inner surface of the bell jar, substantially corresponding to a Faraday shield not-disposed surface of the outer surface of the bell jar.
 4. A plasma processing apparatus as defined in claim 1, wherein the deposition preventive plate is made of an insulator and disposed at a portion, of the inner surface of the bell jar, substantially corresponding to a Faraday shield not-disposed surface of the outer surface of the bell jar.
 5. A plasma processing apparatus comprising: a gas ring forming a portion of a vacuum processing chamber and having a blowing port for a processing gas; a bell jar covering a portion above the gas ring to define a vacuum processing chamber; an antenna, disposed above the bell jar, for supplying an RF electric field into the vacuum processing chamber to form plasmas; a sample table for placing a sample in the vacuum processing chamber; a Faraday shield disposed between the antenna and the bell jar and applied with an RF bias voltage; and a deposition preventive plate attached detachably at least to the inner surface of the gas ring excluding the blowing port for the processing gas; wherein the area of the inner surface of the gas ring including the deposition preventive plate that can be viewed from the sample surface is set to about ½ or more of the area of the sample; and wherein the apparatus further comprises a susceptor made of a dielectric material covering the outer surface and the outer lateral side of the sample table and a metal film disposed on the surface of the susceptor, in which an RF voltage is applied to the metal film to provide the surface of the susceptor with a bias voltage.
 6. A plasma processing apparatus comprising: a gas ring forming a portion of a vacuum processing chamber and having a blowing port for a processing gas; a bell jar covering a portion above the gas ring to define a vacuum processing chamber; an antenna, disposed above the bell jar, for supplying an RF electric field into the vacuum processing chamber to form plasmas; a sample table for placing a sample in the vacuum processing chamber; a Faraday shield disposed between the antenna and the bell jar and applied with an RF bias voltage; and a deposition preventive plate attached detachably at least to the inner surface of the gas ring excluding the an antenna, disposed above the bell jar, for supplying an RF electric field into the vacuum processing chamber to form plasmas; a sample table for placing a sample in the vacuum processing chamber; a Faraday shield disposed between the antenna and the bell jar and applied with an RF bias voltage; and an RF power source circuit for supplying a power source voltage to the antenna and the Faraday shield, the RF power source circuit comprising an RF power source, an antenna connected with the RF power source, a resonance circuit connected in series with the antenna and supplying a resonance voltage thereof as an RF bias voltage to the Faraday shield, a detection circuit for detecting the resonance voltage of the resonance circuit, and a comparator circuit for comparing the resonance voltage detected by the detection circuit with a predetermined set value; wherein a constant of the resonance circuit is changed based on the result of comparison by the comparison circuit.
 10. A plasma processing method for a plasma processing apparatus comprising: a gas ring forming a portion of a vacuum processing chamber and having a blowing port for a processing gas; a bell jar covering a portion above the gas ring to define a vacuum processing chamber; an antenna, disposed above the bell jar, for supplying an RF electric field into the vacuum processing chamber to form plasmas; a sample table for placing a sample in the vacuum processing chamber; a Faraday shield disposed between the antenna and the bell jar and applied with an RF bias voltage; a deposition preventive plate attached detachably at least to the inner surface of the gas ring excluding the blowing port for the processing gas and having an area at least ½ or more of the area of the sample; a susceptor made of a dielectric material covering the outer surface and the lateral side of the plating table, an electrode disposed on the inner surface or on a side of the inner surface of the susceptor and an RF bias power source circuit for applying the RF voltage to the electrode to provide the surface of the susceptor with a bias voltage, the RF bias power source circuit comprising a circuit for supplying the RF voltage power source by way of a variable capacitor to the electrode, a detection circuit for detecting the electrode voltage, and a comparator circuit for comparing the voltage detected by detection circuit with a predetermined set value; wherein a constant of the variable capacitor is changed based on the result of comparison by the comparison circuit. blowing port for the processing gas; wherein the area of the inner surface of the gas ring including the deposition preventive plate that can be viewed from the sample surface is set to about ½ or more of the area of the sample; and wherein the apparatus further comprises a susceptor made of a dielectric material covering the outer surface and the outer lateral side of the sample table and a metal film disposed in the inside of the susceptor, in which an RF voltage is applied to the metal to provide the surface of the susceptor with a bias voltage.
 7. A plasma processing apparatus as defined in claim 5 or 6, wherein the metal film is connected with a conductive portion of the sample table.
 8. A plasma processing apparatus as defined in claim 5 or 6, wherein the sample table is made of an insulator and has, at the inside thereof, an electrode for application of a susceptor bias connected to a metal film with the susceptor is formed in the inside thereof.
 9. A plasma processing method for a plasma processing apparatus comprising: a gas ring forming a portion of a vacuum processing chamber and having a blowing port for a processing gas; a bell jar covering a portion above the gas ring to define a vacuum processing chamber; 